Several aging highway bridges in Clatsop County require significant work to remain viable.

The state Department of Transportation rated crossings of U.S. Highway 101 over Ecola Creek, U.S. Highway 26 over Little Humbug Creek and Oregon Highway 104 over the Skipanon River as structurally deficient in the 2017 report on bridge conditions.

A structural deficiency does not mean a bridge is unsafe, but that it needs significant work to the deck, superstructure or substructure. The rating is used to help rank projects in the state bridge program.

Region 2, spanning the Oregon Coast from Astoria to Florence and the entire Willamette Valley, has slightly more than 1,000 state-owned bridges, more than any other region of the state. Of those, 32 are considered structurally deficient.

Plans are underway to replace the Highway 101 crossing over Ecola Creek and the Highway 26 crossing over Little Humbug Creek in the coming years. Both were built in the 1950s and handle thousands of cars per day.

Both also stand on wooden substructures, along with more than 200 other bridges built in Oregon between 1930 and 1970. Nearly three-quarters of those timber-supported bridges are in Northwest Oregon.

“In the ’30s and ’40s and ’50s, as kind of a cost-cutting measure, there were a lot of timber bridges built,” said Bruce Johnson, the state’s bridge engineer. “Because of the moister climate in Region 2, that timber rots pretty quick.”

The state estimates more than 90 percent of timber bridges have exceeded their designed lifespans of 50 years. Repairing timber has become a major and continually increasing portion of the state’s maintenance resources as the bridges age. Of the 298 distressed bridges in the region, 56 have structural timber elements.

The state is mostly phasing out the use of timber in bridges, replacing elements piece by piece during maintenance until a bridge replacement can be completed, Johnson said.

Daniel McFadden, a local bridge maintenance coordinator whose crews maintain around 400 regional spans, said most of those bridge replacements will be with prestressed concrete, used in most newer bridges. A crossing of Highway 26 east of Little Humbug Creek was replaced in 2014 with prestressed concrete.

“It’s hard to replace with steel here, if it’s not prepared correctly,” McFadden said. “It will rust just like timber will rot.”

Along with maintaining bridges, McFadden’s crews operate draw spans on Youngs Bay, Youngs River and the Lewis and Clark River, some nearly 100 years old.

“I think we’ve done a pretty nice job around here of preserving and maintaining the historic structures,” he said, pointing to the recent work on the decks of the 94-year-old Lewis and Clark and 97-year-old Youngs Bay bridges.

The state has seen an increase in distressed bridges because of their age and new design standards indicating the potential need for weight restrictions.

One of those weight-restricted bridges is the Fort Stevens Highway spur of Oregon Highway 104 crossing the Skipanon River west of Home Depot. The 89-year-old span, formerly a draw bridge raised for logging operations, is restricted from large vehicles such as logging trucks, McFadden said. Plans are being created to repair and paint steel elements in the bridge.

A 2015 analysis by the transportation department of aging highways and bridges projected that deteriorating infrastructure and weight-restricted bridges could cost the state 100,000 jobs and $94 billion in gross domestic product by 2035.

“Portland and coastal communities will be hit hardest,” the analysis said. “As the trade and export hub for the entire state, the Portland Metro region will experience a greater reduction in production than any other region in Oregon. Communities along the coast will also suffer significant losses because it will cost more to move freight to export markets.”

The $5.3 billion infrastructure package recently passed by the state Legislature was meant in part to help stop the precipitous decline in roads and bridges before they face weight restrictions, Johnson said.

“In another year or two, we’ll have big effects on the economy from load restrictions,” he said. “We’re really at a tipping point, and we’ll know in the next year or two whether we can get in front of it.”